ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 605 



3. The same moss, in different habitats, in the same year. 4. Different 

 mosses under similar conditions — that is, in the same habitat and tlie 

 same temperature, with similar water supply, and during the same 

 period. 5. Different mosses in different habitats. The investigations 

 were conducted principally with common, easily observed mosses ; and 

 the results are stated fully and accompanied by illustrations. The 

 principal points are as follows : — 1. Mosses of the same species, in a 

 similar habitat, and in the same year, take about the same time for the 

 development of the sporogonium. Variations are due to differences in 

 the time of fertilization. 2. Most mosses take a longer time for 

 sporogonial development in Germany than in Scandinavia. 3. The 

 length of time does not alter considerably in the course of several years. 



4. The kind of habitat does not materially influence the time of 

 development, though damp places may shorten it somewhat. 5. The 

 growth in thickness of the apex of the sporophyte, which precedes the 

 formation of the capsule, does not begin until the sporophyte has 

 attained its definite length. 6. In mosses with little or no capsule- 

 assimilation the development-time of the sporogonium depends entirely, 

 or almost entirely, on the structure of the stem ; in mosses with great 

 assimilation in the capsule it is dependent as a rule only until the seta 

 attains its full length. Usually the time of development is shorter the 

 better the capsule assimilates, or, when there is no capsule-assimilation, 

 the more sturdy the gametophyte is. 7. The time of development is 

 prolonged when capsule-assimilation is hindered by involucral leaves or 

 large calyptra. 8. The length of the seta has a certain amount of 

 influence on the time of development. Shorter setfe can shorten the 

 time of sporogonial development. 



Spore Mother-celis of CatharinaBa."' — C. E. Allen describes the 

 four-lobed spore mother-cells of Catharinaea. This lobing is almost 

 universal in the Jungermanniales, but does not seem to have been noted 

 in the Bryales. Allen also notes the occurrence of a plastid in each 

 lobe of the spore mother-cell. He finds that the differences in size of 

 spore mother-cells of plants collected in different localities are rather 

 striking ; yet the mother-cells borne in a single capsule differ little 

 in size, and those of different plants growing in the same clump 

 vary but little in size. Along with these differences in size of spore 

 mother-cells of plants from different localities there are other well- 

 marked differences, such as size of plant, size of leaf, number of 

 lamellas on the upper surface of the leaves, and number of spines on 

 the lower surfaces. Some of these characters may be influenced by 

 external conditions, but possibly the plants in question may represent 

 distinct races, included perhaps within the Hmits of G. angustata, or 

 some perhaps merging into G. undulata. 



Pleurozygodon sibiricum.j — I. Gyorffy criticizes the views of 

 Arnell on this species. The latter held that it was most closely allied 



* Amer. Journ. Bot., iii. (1916) pp. 456-GO. See also ' Bryologist, xx. (1917) 

 pp. 64-6. 



t Arkiv. f. Bot., xiv. (1915) pp. 1-3 (1 pi.). 



